Sustaining rotor for aircraft



Sept 5, 1939. T, TH'EoDoRsEN Er AL 2,172,333

SUSTAINING ROTO-R FOR AIRCRAFT lFiled Aug. 25, 193e asheets-sheet 1 JM; f/

Sept. 5, 1939. 4T. THEODORSEN ET AL SUSTAINNG ROTOR FOR AIRCRAFT Filed Aug. 25, 195 9 Sheets-Sheet 2 Sept. 5, 1939.

T. THEoDo'RsEN EVAL SUSTAINING ROTOR FOR'AIRCRAFT Filed Aug. 25, 1936 9 Sheets-Sheet 3 sgae@ Sept. 5, 1939.

T. THEoDoRsl-:N ET AL 2,172,333

SUSTANNG ROTOR FOR AIRCRAFT Filed Aug. 25, 195e 9 sheets-sheet 4 Sept. 5, 1939. T. THEODQRSEN ET AL SUSTAINING ROTO FOR AIRCRAFT Filed Aug. 25, 19:56 e sheetssheet 5 Sept 5, 1939- T. 'rHEoDoRsEN Er AL SUSTAINING KOTOR FQR AIRCRAFT 9 sheets-sheet e Filed Aug. 25, 1936 vSept 5, 1939- T. THEoDoRsEN Er AL SUSTAINING ROTOR FOR'AIRCRAFT I Filed Aug. 25, 193e. sa sheets-sheet 7 Sept. 5, 1939. T. THEoDoRsEN Er AL 2,172,333y

SUSTAINING ROTOR FOR AIRCRAFT Filed Aug. 25, 1936 9 Sheets-sheet 8 i .y 272 i/ u 259w Sept. 5, 1939. 1'. THEoDoRsr-:N Er AL 2,172,333

SUSTAINING ROTOR FOR AIRCRAFT Filed Aug. 25, 1956 9 sheets-sheet 9 i @fm2 Patented Sept. 1939 PATENT ori-ICE SUSTAINING KOTOR FOR AIRCRAFT Theodore Theodor-sen, Hampton, Va.,

ward F. Andrews, Chicago, Ill.

and Ed- Appuminn August z5, 193s, serial No. 91804 41 claims. (ci. 24a-1s)` This invention relates to sustaining rotors for aircraft and particularly to rotors, the blades -of which are flexible in at least one direction so that they may be wound up upon a drum for purposes of storage in compact compass, when out of operation or when only a part of the blades is being used Th'e rotating wing systems -of this invention may be driven by air forces, as in the autogyro, or may be power driven, as in the helicopter, and

l may utilize the inertia of their own rotation toeiect the winding in of the lifting blades upon the drum. l

Many highly desirable results are'attained through the combined aerodynamic and mechanical 'characteristics of this invention. For sustaining large loads with small power, and for good climbing characteristics and slow speed flight, a large span ofthe lifting surface is de sirable. In the case of aeroplanes having rigidy are made highly flexible and damped so as to avoidnatural resonances, the loads are principally tension loads, the bending loads being balanced by the centrifugal force which tends to hold the lifting surface perpendicular to its axis vof rotation. With such a structure large spans may be employed without prohibitive weight. However, such a structure is self-sustaining only as long as it continues to rotate and will fall to the vground when its rotation ceases. To meet this condition we provide means for winding up the rotating flexible blades before they cease ro' tating. This feature has many other advantages which will hereinafter appear.

For high speed flight a much smaller span may be employed lthan for the low speed flight conditions previously referred to; It is advantageous to maintain the aspect ratio or the ratio of the disc area to the blade area reasonably high, and to reducethe span so as to improve the profile drag withrelation to the induced drag for high speed night.

To attain this result the rotating surfaces may bev arranged so that their inner portions may be wound onto the drum and thus taken out of action while the outer portionsA o f the lifting surfaces-continue tofunction as rotating wings of smaller span and area. In this way the rotating wings may be varied in length while flying to meet either the requirements of high speed flight orvof'low Speed and climb,

Another advantage of the flexible construction, and the factvthat the lift, or bending forces exerted `upon the lifting surface, are balanced by the centrifugal force, is that only small spar depth is required for the wing and therefore it can be madev of narrow'chord and thin in section. 'I'his feature presents an advantage over a fixed wing aeroplane where, in many cases, the thickness of the wing is definitely determined by the depth of the spar required to resist thebending moments produced by the lift. It will, therefore, be seen that this invention provides greater latitude in the way of utilizing narrow chords and thin sections.

'I'he possibility of greatly increasing the span of 15 the lifting surface by means of this invention makes it applicable for the construction of large aircraft for carrying heavy loads, as with a large span a smaller expenditure of power is required to maintain the load in the Such large span aircraft, as well as other types constructed ac' cording to this invention, are not subjected to severe stresses due to the sudden changes of air forces produced by violent storms, etc., as are y rigid wings of large span. The flexible and non- '.25 resonant character of the lifting surfaces permit them to yield and yaccommodate themselves to violent uctuations in the air forces without damage, thus enhancing safety and dependability.

Other desirable characteristics, advantages and capabilities of the invention will appear from the following description of preferred embodiments thereof, taken in conjunction with the accompanying drawings, in which:

Fig. 1 is aplan view of an autogyro embodying our invention with an intermediate length of the blades extended, the full extension of the blades Fig. 46 is a transverse sectional detail view taken 50` on line 6-6 of Fig. 4;

Fig. 7 is a transverse sectional detail view taken on line 'I--l of Fig. 4; y

Fig. 8`is asectional view taken on line 8--8 of Fig. ,1, showing, on a larger scale, an air foil means for maintaining the desired angle of incidence of each rotation;

Fig. 9 is a vertical sectional view through a bodiment of our invention;

Fig. 12 is a vertical sectional view taken on.

line `|2|2 of Pig. lil, on a larger scale, showing the blades completely' wound up on the drum;

Pig. 13 is a fragmentary view showingdthe drum in elevation; f Pig. 14 is a sectional detail view taken on line |4|4 of Fig. 18;

Fig. 15 is a sectional detail view taken on line |5-I5 of Fig. 13;

Pig. 16 is a fragmentary sectional detail view. on a smaller scale, taken on line |5| of Fig. 15;

Fig. 17 is a similar view showing theparts in a diil'erent position of adjustment:

Fig. 18 is a vertical sectional view through the lblade'housin'g and drum of a further embodiment of our invention, the blades being shown partially retracted; f

Fig. 19 is a pian view thereof with the upper portion of the housing removed to show the in terior construction; v

Fig. 20 is a fragmentary sectional detail view showing the construction of the blade and its manner of attachment to the drum;

ng. 21 a annuler view snowing the bladepertially retracted for high speed night;

ll'ig.J 22 is atransverse section ofthe blade,

' shown in Pigs. 18 to 21, the section being taken Online 22-22 o! F18. 21;

.f Fig. 23 is s plan view, on a smaller scale, of

conditions; and

the complete rotor structure;

Fig. 24 is av sectional detail view taken on the v une n n-e1- mgm;

Flg. 25 is an elevational view of a further emshowing the relation Fig. 31 is a sectional detail 3|3| of Fig. 29. 1

Referring to the accompanying drawings, and particularly to Figs. l to 8, the autogyro comprises a fuselage 3l, propeller 2|, and conventeken on the une tional landing gear andtail control lsurfaces.

I'he 'complete rotor blade assembly rotates hupon a hollow spindle 22, which is carried by a structure 22, at a suflloientheightabove the fuselage to prevent the blades from fouling any partofthe machine. The flexible blades 39, are carried'by a flanged drum 4|, having-a hub 42, adapted to rotate laround spindle 22, with the aid of antifrlction bearings interposed between the hub and spindle. The housing I4, shaped to obtain the air resistance. consists of an upperA blade with respect to its plane of bodiment of our invention, with the bladesvound surface under' high velocity upon the rotor blades member '25, having a centrally located downwardly projecting nange 48 and a lower member 25, provided on its under surface with a ring gear 45. The housing 24, with the aid of antifriction bearings, rotates freely around hub 42 of drum 4|. A series of pulleys I8, circumferentially spaced around the periphery of drum 4|, are free to rotate on shafts 2l carried by members 25 and 38 of hous 24. Slots 4l, at the periphery of the housing 34, are provided for housing.

Each of the blades Il is provided at the inner end with a loop whereby it is secured to the drum 4| by means of a bolt 5l, each bolt passing .through the loop of one of the blades 29.

s brake bend sl 1s carried by the nu n of drum 4| and ls adapted, when expanded, to engage the flange 42 of the housing 34.

- the passage of blades 29 into and out of the A brake bands 5| and 52 are capable of being actuated n alternately by means of a vertical shaft 55, which extends through the vhollow spindle-32. This shaft carries conical cam surfaces which are oppositely directed. Thus, when the shaft 55.is

.projected upwardly the brake band 5| is exhousing 54 to rotate freely around hub 42 of the .drum 4|, and brake band 52 is expanded. thus locking drum 4| to the spindle 22 and holding' the drum stationary. When rodl 55.is in the intermediate position, neither brake 5| nor 52 is applied.

'lhe housing 24 is driven by an engine through shaft 4I. A clutch 45, adapted to be engaged or disengaged'by the operator, connects the shaft 48 to shaft 41 which carries a pinion 44 in mesh with the ring gear carried by housing 34. A

The operation of extending the blades when they are fully wound up on drum 4| is as follows: The rod 55 is moved to its upper position,

locking-housing 24 to drum 4|, and the clutch u n engaged se that the engine wmdrlve housing 24.' The direction of rotation, as viewed in Fig. 3, is clockwise. When housing 34 is rotating atthe desired speed, the rod 55 is put in intermediate position, thus permitting the drum 4| torotate independently of housing 24. The centrifugal force acting on blades 29 will then unwind them ofi the drum 4|, the drum rotating ata higher speed. than housing 34 while the unwinding continues. .The rate at which the blades unwind from the drum may be controlled..

by an upward pressure on rod 55, to restrain the rotation of the drum 4| relative to the 'housing 24. The blad may be permitted to-unwind to their full extent or they may be stopped atany intermediate point by pushing upwardly on rod 55, thus locking'drum 4| with housing 24. After the blades are unwound and the machine is in night, the clutch 45 may be disengaged/.wherewill be driven-by air forces. .Towlndupthebladeaclutch l' 'being disen-l (Due to the inertia of the rotating blades they will continue to revolve, together with housing 34, around drum 4|, thus winding themselves onto the drum. During flight the length of the .blades may be reduced in this way to any desirable degree for the purpose of high speed opera- `tiom and, when required, the length of the blades may again be increased for landing and low speed operation.

Preferably blades of short chord are employedv vblade area can then be obtained by providing a sufficient number of blades. By using blades of short chord the torsional load upon the blades is kept small. This embodiment of the invention permits the blade to be wound up with its chord parallel to the axis of rotation during operation and permits all the blades to be wound up on a single drum.

v'Ihe construction of the blades 39 shown in this embodiment of the invention will now be described. The blade is of suitable air foil section, as shown in Figs. 5, 6 and 7. The blade is of a flexible structure and preferably comprises a flat cable 51which may be of steel, in the leading edge of the air foil section and a similar cable 56 located near the trailing edge of the section. The air foil section may be formed by an upper memberv 59 Iand a v lower member 66, both of which may be of molded rubber and fabric.' Both sections comprise exterior skin portions 6| and 62 which merge at their forward and rear ends into substantial solid portions 63, 64, 65, and 66, respectively, within which portions the4 cables 51 and 56 are embedded. At intervals along the length of the blade rigid transverse spacing members 61 are provided which abut against the forward and rear cables 51 and 56.` The spacers 61 are embedded within webs of rubber which extend between the skinportions 6| and 62. Between the spacers 61 the skin portion 61| and 62 are preferably provided with rubber webs 69 which register with each other and serve to preserve the air foil-section of theblade. sembling the blade, the metal portions 51, 58 and 61 are placed in the upper portion 59 within the formations provided for them. The lower section 68 is then placed over the upper section and the two sections are cemented or vulcanized together so as to provide a single unitary structure which isj flexible in its spandirection', but which is reinforced against distortion of its air foil section. At the outer end each blade 39 is provided with a small air foil section 66 spaced a substantial distance rearwardly of the trailing edge of the blade land rigidly supported therefrom by means of streamlined booms 69. of booms 69 are enlarged and weighted to provide a concentrated weight at the end of the blade sov that, under the action of centrifugal force, the blade will be in tension and take the lift properly. The air foil section 66 is xed at an angle to the chord of blade 39 such that, with the air forces acting on air foil 66, the blade 39 will have the desired angle of incidence. angle ofincidence of the blade at the other end is determined by the angle of slot 46 relative to to the plane of rotation.

The weight 16 is so proportioned as to counterbalance the weight of the tail-surface 66 so that the blade will not tend to twist under the influ- In asy The forward ends 16 r.

ence of centrifugal force. In other words, the radius through the blade will coincide with the center of gravity of the whole tip unit, including weight 16, booms 69 and tail plane 66. The relative angle betweenjthe planes 39 and 66 establishes the angle of attack of the blade 39. This angle of attack will then tend to remain constant with relation to the relative air flow. If the aircraft sinks vertically the relative air flow will slant upwardly relative to a plane perpendicular lto the axis of rotation. If the rotational speed of the blades increases, the angle of the relative air flow to this plane willbecome less, but the tail surface will tend, at all times, to maintain the same angle of attack of the blade 39 to its relative air iiow.

The ends of the blades may be weighted in such a way that the centrifugal force-exerted on the cables 51 and 58 may aid in resisting torsion. In the case of a normal air foil section where the center of pressure is nearer the forward than the trailing edge, we prefer to concentrate the weight nearer the forward edge. 'I'his may be done conveniently by associating a relatively large weight 242 (Fig. 6) with the forward cable spindle 1| by means of anti-friction bearings. The hub 12 fcarries a downwardly projecting flange 62` provided with gear teeth 14. A series of flanged drums 66 having gear teeth 6| cut on their flanges are positioned radially around the worm gear 13 and mesh with it. The drums 66 rotate on shafts 98 in bearings 99 supported by the arms 15, 16, 11 and 16. The arms 15 and 16, one on each side of each drum 80, project radially from the hub 19. The arms 11 and 18 are similar and are rigidly secured to the lower hub 83, which iiange also carries a ring gear 64 atits lowennost end. At their outermost ends the arms 15, 16, .11 and 18 support shafts 66 on which rollers 65 are rotatably mounted. The adjacent outer end s of arms and 16 are connected together by a transverse member 61 and the adjacent outer ends of arms 11 and 16 are connected by a similar member 66. Adjacent radial structures, each comprising the arms 15,

16, 11 and 18 and the members 81 and 66, are tied together by rods 89 which are located adjacent the periphery of the assembly. Each pa'ir of rollers 85 determines the angle of incidence of the blade 39 which projects therebetween, these rollers being provided with a small angle relative to theV plane of rotation ofthe blade housing.

The arms 15 and 16. 11 and 18. the hubs 19 and 63 and the members 81, 86 and 69 form a unit 68 wh'ch is rotatably mounted on hub 12 by means of anti-friction bearings.' This unit carries the drums 68 and the rollers 65.v The driving of the unit 96 is accomplished by pinion 9| meshing with gear 64. Pinion 9| is mounted on the shaft 92 which is rotatably ,mountedin a bearing 49 3 supported in the-base of thehollow spindle 1|. A shaft 94, driven by an engine, drives shaft 92 through a disengaging clutch 95, which clutch ls operated by a rod 96. A gear 91 is also mounted on shaft 92 and is free to rotate thereon. This 12 will rotate, and the worm will rotate at a speed higher than the unit 22.

The rotating unit 92 is enclosed in a housing comprising van upper casing ,member |22 and a lower casing member |22, the casing members.

beingvformed to present the minimum air resistance. The housing thus formed leaves openings in alignment with the bite of the rollers 22 forv the extension of the blades 29 out of the housing. An expanding brake band |22 is carried by the spindle 1|, and is adapted when expanded to engage the inner surface of flange 22 on hub 12.

The brake band |24 carries rods |22 projecting l inwardlyI into the interior of spindle 1| and these rods are adapted to be engaged by a conical, cam

|22. The c'am |22 is carried on the upper end of a rod |21 and is operated by axial'movement of this rod. When the rod |21 is in its lowermost position, the hub -12 is free to rotate around the spindle 1|. When, however, rod |21 is pushed upwardly, the brake band |22 is expanded against the inner surface 4of the iiange 22, thus locking the hub 12 to the spindle 1 I and holding iti-against rotation.

The blades 22 are similar to those shown in Figs. 4, 5, 6 and '7, and each blade is fastened to the hub of one of the drums 22. If the blades are in the fully retracted position they are projected outwardly in theVK following manner: 'I'he clutch |22 is disengaged and clutch 22 is engaged and the shaft 22 is driven. The hub 12 and worm 12 are caused torotate, and the rotating unit 22 and its housing being i'ree to rotate, are put into rotation by the worm 12. The clutch |22 is then engaged, thus locking gear 2| to shaft 22. The vhub `12 and worm 12, and the rotating unit 22 are now being driven directed in' the same direct tion, but the hub` 12 is driven at a considerably higher speed than the unit 22. Thus, there is relative rotation between the worm 12 and the drums 22, with the result that these drums are trotated on their shafts 22 and the blades 22 are unwound. The blades may be permitted to unwind until they are completely extended or may be stopped 4at any intermediate position by disengaging the clutch |22. Owing to the non-reversible drive between the worm 12 and the drum gears 2| there is no' risk of the blades extending further after the clutch |22 is disengaged. To retract the blades the clutch |22 must b disengaged. The rod |21 is then pushed upwardly, thus locking hub 12 and worm 12 to the spindle JI and holding the worm stationary. 'I'he unit 22 continues to rotate, either due to inertia of the` rotat'ng system or by power drive through pinion 2|. Thus the drums 22 rotate about the -stationary worm 12 and are caused to rotate their shafts 92 in the direction for winding up the V blades n.

unwinding of the blades. Each blade is carried on an individual drum and unwinds exactly thev same amount as each .other blade at any time, so that the exact balance of the rotating system will be maintained whenthe blades are only par envases' tially projected for high'or intermediate speed travel.

Figs. 1l to 17 inclusive illustrate a further embodiment of our invention. In this construction a tWO-'bladed rotor is ,provided which is Wound 5 up on a single horizontal drum II2. Each blade consists of two cables II2 and I I I attached to the" outer ends of the drum II2 and convergingY atA Y their outer ends'. Between the outer portions of cables I I 2 and |I| a solidair foil section II2 1 is formed of a flexible material such as rubberized fabric with suitable stiilening members. The cables I I2 and I I, supporting the air foil sections II2, are also of air foil section and consist of steel wire cores covered with a suitable flexible material to give them the desired air foil shape. If desired, the air foil section II2 may be made longer and may extend inwardly to a point close to the drum II2. The drum is. of course, formed to receive it. y

At their outer ends the blades I I2 carry weights T29 attached to the end of cables II2 and III. The comparatively wide spacing of the cables II2 and and the separation of their points of attachment to the drum from each other and from the axis of rotation operate to keep the section at the proper angle and to resist any tend- 'ency of the blade to twist or curve duringpperation. 'Ihese features also aid materially in maintaining the blades in radial relation if they are power driven from the hub as in helicopter operation.

The drum I I2 is composed of two parts I I4 and II2 carried'on a shaft II2 and free to rotate thereon. As best seen in Figs. 13 and i4, the adjacent portions of the parts II2 and IIS of the drum I I2 are enlarged, as shown at I I9, and their remote end portions are reduced as shown at |I1 and II2. The surface of the drum I I2, between the enlarged central portion |I9 and the reduced end portions ||1 and ||2,consists of spirals |22 which start at the small diameter ends ||1 and I I2 of the drum and travel longitudinally towards the center ofthe drum to the large diameter II2. The purpose of the spirals |22 is best illustrtedin F18- 12, Where the blades are shown fully wound up. It will be seen that the cables II2 and III wind up on the spirals |22 thedrum II2, with the cable I |2`of one blade and the cable I I I of the other blade overlapping. The wing'section I2 winds up on the cylindrical central portion II2 of the drum in the manner shown. In this manner the blades are wound up in the smallest compass and are positively supported on the drum along their entire length. It will be understood that during flight the blades are completely unwound and that the drum itself presents relatively little air resistance.

At their` adjacent ends the drum parts I I4 and II2 are provided respectively with a recess |22 and projections |22 extending thereinto. Thus these parts II2 and IIS may rotate independently of each other to'a limited extent; but when rotated to that extent, "the projection will come into contact with an end of the recess |22 and the drum will turn as a whole with shaft I I2. To reduce the weight of the drum II2 the parts II2 and II2 are made hollow, as shown at |21. Tire adjacent ends of the drum parts II2 and II5 are recessed, as shown in Fig. l2. Within these recessesopposed bevel gears |26 and |21 are rigidly secured to the drum parts I|4 and IIS respectively. Bevel pinions |28 are interposed between bevel gears' |22 and |21 and mesh therewith. An

annular ring |22 is rigidly mounted on the shaft 72 which the pinions |28 are rotatably mounted. If

the shaft 6 is locked in a stationary positionv and the drum part I4 is rotated in one direction, the drum part ||6 will rotate in the opposite direction. If the shaft ||6 is locked to the drum part H5, then rotation of drum part ||4 will cause both hubs to rotate in the same direction 'as a unit. f

The shaft ||6 is carried by bearings |32 and |33 supported from a hub |34 by arms |35 and |36. The shaft 'is free to rotate within tl'e bearings |32 and |33, and rigidly carries a disc |31 which is positioned between the end of drum part 5 and the bearing |33.y A bevel gear |38 is rigidlymounted on the end of drum part ||4 adjacent the bearing |32. A radiallyprojecting guard disc |39 is carried on the end of drum part ||4. 'I'he gear |38 and guard disc |39 are rigidly fixed to drum part ||4 and rotate with it as a unit. 'Ihe hub 34 carries a large spur gear |40 at its lowermost end and is rotatably mounted by means of anti-friction bearings |4|, on a supporting spindle |42. The spindle |42 carries an enlarged spherical portion |43 below the gear |40. A socket member |44 encloses the spherical member |43' and is rigidly secured to the body of the aircraft. This ball and socket joint 'permits the operator to tilt the complete assembly in any direction for proper control' of the aircraft.

The base of the spindle |42 rigidly carries projecting arms |46 above and below the socket member |44. These arms support a bearing in which a shaft |41 is rotatably supported. At its upper end the shaft |41 rigidly carries a pinion |48 which meshes with the ring gear |40. The lower end of shaft |41 carries a disengag'ing clutch |49, operable by a rod |50, and adapted to connect the shaftl |41 to a drive shaft |5| which is driven fromthe engine. A central tubular shaft |52 is mounted for free rotation in the spindle |42 by means of anti-friction bearings |53 and |54. carries a bevel pinion |55 and at its lower end a brake drum |56. The end of the spindle member |42 adjacent the brake drum carrieaa contract-` ing brake band '|51 adapted to engage the outer surface of brake drum |56. 'I'he brake band is operable by rotation of a rod |58. The spindle |42 also carries a brake shoe |59 adapted to engage the inner surface of brake drum |56 and operable by rotation of a rod |60.

The arm |35 carries four spaced stub shafts |6|. Upon these shafts are rotatably mounted gears |62, |63, |64 and |65 whichmesh with each other in the order stated ,to constitute a gear train. 'I'he gear |62 is integral with a bevel gear |66 which meshes with the bevel gear |55. The gear is integral with a bevel gear |61 which meshes with the bevel gear |36. Casing members |68 and |10 are provided to enclose the gear mechanism and may be shaped as desirable for minimum air resistance. y

Now, with brake band |51 and brake shoe |59 in the released position, and the hub |34, together with its accompanying assembly, rotating in a clockwise direction as viewed from the top, the shaft |52 and brake drum |66 will also rotate at the same speed and drum ||2 will remain stationary with respect to the hub |34 and supporting members |36 and |36. When, however, the brake band |61 is contracted and shaft |82 is locked in a stationary position, the continued rotation of the hub |34 and its assembly the supporting member At its upper end the shaft |52 relative to the pinion 55 will operate through gears |66, |62, |63, |64, |65, |61 and |38 to rotate drum I2 about its axis in a counterclockwise direction, as viewed from the left in Figs. 12 and 13. When brake |51 is released and brake shoe |59 is operated, the effect is the same except that, due to the limited friction available by application of brake shoe |59, the shaft |52 and pinion |55 will continue to rotate, but at slower speed than the hub rotate at a slower speed than with brake |51 applied.' It will be seen that the brake shoe |59 can be dispensed With and the brake |51utilized for the purpose by providing for light and heavy application of this brake.

A bell crank lever |1| is pivotally mounted on |36 below the bearing |33. A locking pin |12 is slidably mounted in an opening in the arm |36, parallel to shaft ||6. This pin is operatively connected to one end of the bell crank lever |1|. The disc |31, which is -integral with the shaft |3|, is provided with any |34. In this case the drum |2 will |12 toward the disc |31. vThe end surface of drum part I5 adjacent the disc |31 is provided with a series of openings |14, |15 and |16, located in angular relation and equidistantly from the center of the drum. The openings |14, |15 and |16 are adapted to register with opening |13 in disc 31 as the drum part ||5 rotates on the shaft ||6. Within the opening |14 is slidably mounted a pin |11 which is yieldably pressed outwardly against the surface of the disc |31 by means of a spring |18 also located in the opening |14. The pin |11 carries a radially projecting stud |19 which operates in a slot in the drum part |5. In on'e extreme position, as shown in Fig. 12, the stud |19 abuts against the surface of disc |31 and prevents the pin |11 from projecting disc. In its other extreme position, Fig. 16, the stud |19 abuts against the inner end |8| of the slot |80 and the pin thereby from moving further into the drum part ||6. 'Ihe bell crank lever |1| is actuated by a flexible cable |82l operating in a4 casing |83. 'I'he cable |82 and its casing |83, extends through the arm |36 and the hollow shaft |52, and thence to a position convenient to the operator. In order to provide for the rotation of the casing |83 with the shaft |52, a swivel |84 is provided at the lower end of the flexible cable |82.

The supporting cables ||6 and of one blade are attached to drum parts ||5 and ||4 respectively, as shown in Fig. 13. The cables ||0 and of the opposite blade are attached in like manner to the opposite side of the drum parts |'4 and |5 respectively.

'Ihe operation is as follows: As shown in Fig. 12, lthe blades are initially in their fully retracted position, being wound up on the drum ||2. The cable |82 is pulled downwardly, retracting pin 12. The drum part 5 is then locked to the beyond the as shown in |11- is prevented shaft ||3.' The brake weights |38 at the tips of the wound up blades ||3 will pull them of! the drum ||2. Drum |I2 will rotate around its longitudinal axis, thus driving shaft |32, relative to the hub |34, through gear |33; pinion |33, and the gear train therebetween. This will continueuntil the blades arel fully extended, when drum I l2 will cease to rotate and shaft |32 will rotate with the hub |33. The rate atv which the blades unwind may be controlled as desired by a partial application of the brake |31 ofthe brake shoe |38, which will retard the rotation of shaft |32 with 4a corresponding effect upon the rotation of drum 2. After the blades are fully extended the exible cable |32 is released and spring |83' operates the bell crank lever |1| to move the locking rod |12, placing the parts as shown in Fig. 16, and so locking disc |31 and shaft |`I3 against rotation lin bearings |32 and |33. At the same time the drum part ||3 is unlocked from disc |31 and the drum parts ||3 and ||3 are free to rotate in opposite directions to a limited extent on the shoe |33 is now applied by Vmeans of rod, |33, placing a definite retarding lin a stationary position.

effect on 'the shaft |32 and pinion |33 and thereby driving the drum part ||3 in acounterclockwise direction, as viewed from the left of Fig. 12, andataslowrateofspeed. Thedrumpart ill, rotating in a counterclockwise direction, drives drum part ||l in the opposite direction (counterclockwise as viewed in Fig. 14) through the gear assembly |23. This rotation continues untilthe opening |13, in the end of hub H3, registers with the locking pin |12, whereupon pin |12 will ba forced into the opening |13 by the spring |83' as showninFlg. 1'1, and the drumpart ||3 islocked The shaft ||3v being locked by thepin |12, the gear assembly |23 locks the drum part Ill against rotation. vIf the pin 12 is held out of the opening |13 and the action 0f the brake |33 is continued, the pin'l12 may be caused to enter the opening |13 and lock the drum parts ||3 and ||3 in a diiferent relation. Fig. 13 shows, in full lines, the position of cables ||3 and ||I as attached to hubs ||3 and ||3 after the blades are fully extended'and before the drum parts ||3 and||3 have been moved.- relatively as above described. The cables ||8 and are shown in dotted lines in the position they occupy after the relative movement.- It will be seen, in Fig. 13, that cable ||8 is moved downwardly and cable upwardly with respect to the axis of rotation. In this manner the wing section ||3 is given the desired change in its angle of incidence. When pin |12 engages opening |13 in the'drum part H3, the angle of in-- cidence is maximum, and when the pin engages opening |13 an intermediate vangle of incidence is secured. When pin |12registers with pin |11 or opening |13 the 'angle of incidence is at a minimum or zero.

It is to be noted that the blade other than that shown in Fig. 13, having its cables ||3l and attached to the drum partsV ||4 and ||5`re spectively, is orientated in the same manner by the relativemovement of thedrum parts ill and H3. When the pin |12 is withdrawn by o the cable |32. the centrifugal force on the blades brings the. drum parts Ill and ||3 into initial relative position andthe pin |11 automatically enters theopening ||3inthe disc |31 andlocks the drumpartstotheshaft ||3 ininitial relative position.

Duetothepossibleanglechangeprovided the angle best suited to slow speed. climb, high speed engine 'stantial degree when arva'ssa and either for'autogyro or helicopter operation, may be selected. The displacement of the anchorages of the blades tends to change the angle of incidence of the entire lifting surface and hold it fixed with relation to thev axis oi' rotation.

This construction is adapted to take ofi' as a helicopter in the following manner: The blades are completely unwound and are rotated by the up to a speed higher than normal, the angle of incidence of the blades being at or near zero, 'Ihe angle of incidence of the blades is then increased to the maximum in the manner described above. The increase of angle will cause the ground as a helicopter. After sufiicient elevation is attained, thehaircraft may be driven forward in usual manner and the blades may be allowed to function as autogyro blades. If it is desired to operate in this way, the opening |13 in the drum part ||3 should be located remote from the opening |13 in order to provide a large angle of incidence for the helicopter operation of the blades. The opening |13 should be located to give a small angle of incidence so that the pin |12 may be en operation, to permit the blades to function as an autogyro.

Owing to the fact that theforwal'd cable is connected to the rotating assembly at a substantial distance from the axis of rotation, the centrifugal force tends to resist torque to a subpower is applied continuously to the rotating assembly for permanent helicopter operation.

To retract the blades the iiexible cable |32 is pulled downwardly, disengaging locking pinl |12 from opening |13 or |13. The tension on the cables and due to centrifugal forcel acting on the blades, will rotate the drum parts ||3 and ||3 into their normal position and the pin |11 enters` opening |13 in disc |31.'as shown in Pig. 12. The brake |31 is applied by rotation of rod |38, thus locking shaft |32 and pinion |33-in a stationary position. As hub |33 continues t0 rotate, due to inertia ofgthe rotating orby power drive through shaft |3|. drum ||2 is rotated in a counterclockwise direction. as viewed from the `left of Fig. l2, through gear |33 and |55 and the intermediate gear train, thus winded'thereinto, alle! the helicopter l ing up the blades by the energy of their own mog mentum.

A further modification of our invention is illustrated in Figs. 18 to 24 inclusive. The rotating system |83 is supported on a tubular spindle |33 which is attached to the fuselage of an autogyro or helicopter and supported at a suitable height above it. A A hub |31 is rotatably mounted'on the spindle |83 by means of anti-friction bearings and at its lower end carries a flange |33. The flange |88 carries gear teeth |33 on its outer surface, and its inner surface is adapted tov be engaged by an expanding brahe band |33 carried by the spindle |33. The brake band |33 carries rods |8| -which project inwardly into the interior of the spindle |33 and are adapted to be engaged by a conical cam |32. The cam |32'is carried on the upper end of a tubular operating member |33 adapted to move vertically in Aa bearing |33 carried-by the base of the spindle |33. The hub |31 carries a means of radial members |33. The' rotating sysftem is driven by a pinion |31 which meshes with the gear |33 carried by hub |31.-Thepinion |31 threaded drum |33 byA 'Ihree rotor blades are shown in this embodi ment of our invention. Each blade is composed of a plurality of sectional assemblies 204 placed end to end. Each section assembly 204 consists of a tubular member 205 carrying a pivot member 206 at each end. Each member 4205 rigidly carries forming members 201, of desired air foil shape, at each end, .and at suitableintervals therebetween. The forming members 201 are connected at their forward ends by members 208 forming a solid leading edge for the blade, and at the rear end they are connected by 'members 209 which form the trailing edge of the air foil. 'I'he sectional assemblies 204 are pivotally connected together by pins 2| 0 passing throughfthe pivot members 208 of each two adjacent" assemblies. The sectional assembly 2|| adjacent the point of attachment of the blade to the drum |95 comprises two parts connected together by a horizontal pivot 2|2 carried by the tubular members 205. Similar sections 2|| may be placed at intervals along the blades, thereby giving the blade a degree of flexibility in a direction perpendicular to the plane of rotation of the blades. Pivot members 206 operating around pivot pins 2|0 provide the necessary degree of flexibility in the plane of rotation to permit the winding up of the blades on drum |95. The entire blade assembly is covered with a exible material, such as elastic rubberized fabric, to form a casing 2| 3 over the entire blade, which casing is fixed to sections 204 at a suilicient number of points to resist the action of centrifugal force tending to -pull casing 2|9 oil. the blades.

The pivot joints lbetween adjacent sectional assemblies 204 may be given a desired degree of damping by means vof spring friction members. As seen in Fig. 24, the pivot members 205 of one section assembly 204 are interleaved with the pivot members of the adjacent section assembly, and frictional spring washers 231 are interposed between the pivot members to provide the dampins.

The center of gravity and the elastic axis of the blade should substantially coincide and should be located close to the aerodynamic center of the air foil section of the blade, and the section should have a small center of pressure travel.

An advantage of' this embodiment is that, al-

though the blade has flexibility in the plane'of rotation and perpendicular thereto, it nevertheless has considerable torsional stiffness which makes it possible to flx the angle of incidence ot the blade relative tothe axis of rotation. This results in a reduction ofthe effective angle of incidence on the sidey of the rotor traveling up wind and, therefore, having. the greatest lift.

This effect tends to equalize the' lift on either.

side of the center of the span axis of the rotor. The sections and joints should be constructed Y so asv to have the maximum torsional rigidity and tensile strength as these are substantially the main loads to which they are subjected.

In the construction shown, three blades- 2|4, 2|5 and 2|5 are attached t'o the drum |95 by means of pins 2|'|. The outer surface of. drum .'95 is grooved in the form of a triple thread 2|8 beginning at the upper end of the drum and travelling downwardly. In this manner each blade is provided with an individual groove into l of the blades. 'undercut as at 220 to accommodate any excess which it' may be wound. The grooves 2 I8 are cut inthe drum |95 in the shape of a polygon having sides 2|9. The length of the straight portions 2|9 of the polygon are of the correct length to accommodate vone of the sectional assemblies 204 The corners ofthe polygon are material of casing 2li due to the angle-the adjacent blade section assemblies 204 assume when wound up in the grooves. As seen in Fig. 18, the grooves 2|8 are shaped to conform to the leading edges of the blades. Flexible casings 22| and 222 are provided to house the drur'n |95 and to minimize the air resistance of the rotating assembly |85. Upper casing member 22| is carried by the uppero end of drum |95 and lower casing member 222 is carried by the lower end of the drum. The casings are so constructed that, as the blades travel vertically along th'e drum as they are wound or unwound, the outer edges of casings 22| and 222 will remain in resilient contact with the blades and follow them as they move up or down.

To unwind the blades fromv their fully retracted position the rotating assembly is driven through pinion |91 by power shaft 200 through the clutch 20|. The rotating assembly |85 will then be rotated in a clockwise direction as seen in Fig. 19 and the blades 2|4, 2|5 and 2|5 will be carried out and unwound oif the drum by the action of centrifugal force. AWith the blades fully extended, high lift is realized which is suitable for take oi, lslow speed flight and landing. For high speed flight it is desirable to reduce the effective diameter of the rotor blades. For this purpose we provide latches 223, one for each blade, pivotally mounted on shafts 224 carried on the interior of the drum |95, at points corresponding to the desired projected length of the blades. The blades 2| 4, 2|5 and 2|9 are partially the wall or' the drum |95, engage avpivot pin 225 which projects slightly above and below the outer casing of the blade. The sectional blade assemblies 226 and 221 adjacent this pivot pin are constructed with forming members 228and 229 at such an angle that the projecting part of the blade 203 may pivot around the pin 225 to a position nearly perpendicularto the blade section 226, as seen in Fig. 21. The sectional assembly 221 is providedwith a vertical pivot 2|2 in the same manner as the assembly 2||. 'Ihus it will be noted' that in either the fully extended or partially extended position of the blades a vertical pivot is provided close to the point vof attachment of the blade to the drum. This is desirable in order to transfer the lift developed by the' blades as directly as possible to the drum and lto elimi.

nate any undue bending strains on the blades.

Although only one set of latches 229 is shown here it will be understood that additional latches may be employed to provide additional operating positions of the blades. Also, similar latches may be provided for locking the blades in the fully .wound up position for storage purposes. At the outer end of the blade a section of some length may be left unjointed. This'part yof the blade 288 can then be shaped into the most suitable air foil section for low drag at the comparatively high speed obtained at the tip of the blades.

The latches 228 are actuated by cranksl which are carried by the hub |81 on pivots 29|. The cranks 288'are disposed radially around hub wound up on drum |85 and the hooked ends of latches 228, which project through openings in |81 and, at their lower ends, -are connected to 75 latches m by unie m. 'rhe upper ends m or lar member |53 and at its upperend it carries a cylindrical plug 235 adapted to engagethe ends Springs 2 hold latches 233 of the cranks 235.

' 223 in latching engagement with the pins225 on the blades. Centrifugal force, due tothe rotation of drum |55, augments the action of the springs 235 to hold latches 223 in `engagement with pins 225. Thus; when operating rod and plug v235 are in the downward position, latches 223'will remain inv engagement with pins 225. However, when rod 234 and plug 235 are actuated upwardly, latches 223 will be moved out of engagement with pins 225 and the blades will be permitted to unwind to their full extent.

When taking off, the clutch is engaged and tbe rotor assembly |55 is rotated through the pinion |51 andthe gear Ill The blades will unwind,iftherod234 is initslowerposition,to proper length for high spe'ed operation or, if rod 234isinitsupperposition,totbeirfullextent for high lift and slow'speed. The rate at which miiting the remainder of the blades thus obtaining thebladesunwind fromtbedrummaybecontrolled by throttling the engine or by disengaging the clutch 25| and allplyln the brake |55. The rod 234 should be in the lower-position. After the blades have been unwound .to the high speed pomtion. the clutch 25| is-again engaged and therotating system brought upto speed. Thenclutch 25| is disengaged and rod 234 pushed upwardly. thus releasing the latches 223 and vper- Y to unwind. the brake |55 being applied as necessary to pre- 'vent the blades from unwinding too quickly.

After the blades are fully unwound.v the clutch 25| is again engaged and the blades brought up to speed. When the machine is in ilight'the the length of the projecting blades is reduced to the high speed position by disengaging clutch 25| and applyingbrake |55 by an upward movement ofthe tubular member |53. This retards the ro*- tation ofdrum |55 and causesthebladesto` wind themselves around the drum due to their yown momentum.' The rate at which the blades wind up on the drum may be controlled by varying the degree of application of the brake |55.

Whenthe bladesarewound upto thepointwhere latches 223 engage pins 225 in the blades. the brake '|55 is released. At any desired time in flight the blades may be released to their full extent by' merely moving the operating rod 235 uphigh lift for purposes of slow speed flight, climb. or landing.

Especially for helicopteropention we prefer to mount compression springs 235 between adjacent assemblies 254 near their trailing edges and to .increase the damping of the hinge joints. We

also provide springs 244 between the innermost assembly 2'|| and an abutment 245. The springs 235 and 244 aid materially in imparting yielding rigidity to the blades in the plane of their rotation and opposite to their direction of rotation,

enabling them toresist a considerable torque ap- 1 plied at the hub when they are positively driven @in helicopter operation. 'f be springs 235 preferably decrease hub. In unwinding the oppose the in strength outwardly from the blade,tbesespringsalso the ' in a generally circumferential andtherotoiblaalles- 4outvof the Hades and aidmaterlallyinpreventlngtoorapidunwinding on the air craft in a generally perpendicular direction. A sleeve 241 is rotatably mounted on the standard 245 'and carries at its upper end a vlrorm`245v and at its lower end a gear I245. A sleeve255 is rotatably mounted on' the sleeve 241. At its lower end the sleeve 255 gear 25| which meshes with a carried at the upper end of a shaft 253.

pinion 252 rigidly The shaft 253 is rotatably supportedin the base of the standard 245, and is adapted to be connected by carries an annular a clutch 254 to a shaft 255 driven by the engine (not shown). The clutch '254 is adapted to be en- Y gaged and disengaged by a manually operated shaft 255. s

A gear.251, which is freely mounted on the shaft 253, meshes with the gear 245. The gear 251 may be clutched to the shaft 253 by a clutch 255, manually'operable by rod 255.

'lhe sleeve 255 is provided on opposite sides with upwardly diver'ging arms 255 which provide bearings 25| at their upper ends for freely rotating shafts 252'of drums 253. These shafts lie direction with rebut they are despect to the axis of rotation.

flected upwardly out of the horizontal in the direction of their travel by a small angle to impart the proper angle of incidence to the blade carried by their drums, asbest seen in Fig. 26. The upper end s of the arms 255 at adjacent ends of the drums 253 Aare connected by tension members 254.

Adjacent ends of the drums 253 have rigidly moimted thereon worm `gears 255 which mesh with oppositely directed ried by a transverse shaft 251. The shaft 251 is rotatably supported near its ends in brackets 255 carried bythe adjacent arms 255 and near worms 265 rigidly carits center by brackets 255 carried .by the sleeve.

255. v Between the brackets 255 the shaft 251 has rigidly mounted thereon a worm gear 215 lin m I withfthe lworin 245. It will readily be unders that when the worm 245 drives the gear 215 in one direction, the drums 253 are driven in opposite directions, and that these directions may be reversed by reversing the relative rotation of the worm 245 with respect tothe gear 215.

The gear 245 is recessed on its underside and a brake band 21| is mounted in the recess. 'l'.he brake band 21| may be applied by a manually operated rod 212 so as to arrest or retard the rotation of the sleeve 241.

The drums 253 are preferably polygonal'. for example, hexagonal shape as best shown in Fig. 25, and the blades 213 which are mounted there'- on suitably consist of a series of rigid sections^214 pivotally connected together by transverse hinges 215. 'Die blade sections 214 are arranged to fold up on the polygonal drums 253 and for thisv .211, 215 and 215 are enclosed Within-'a 118141 shell 15 l233, and all the sections of the blade 213 are enclosed within a exible covering 28|.

The innermost section 214 and several of the other sections, particularly some of those near the inner end of the blade, are made of two parts connected together by pivotal connections. 282, the axesof which are generally parallel to the axis of rotation of the sleeve 258 when the blades are projected in the horizontal direction. The pivotal connections 282 are preferably high friction connections generally similar in effect to the pivotal connection shown in Fig. v24. 'I'he play in the joints 215 should be kept as low as practicable. The tension applied to the blade by centrifugal force aids materially in minimizing the eect of any play present..

In order to reduce air resistance we prefer to provide a streamlined housing 283 which may be supported on the arms 268. 'Ilie housing 283 projects on either side beyond the drums 263. If the rotor is intended principally for high speed flight with the blades only partly extended, the housing should be arranged to enclose the portions of the blades remaining on the drums. 'I'he housing 283 shown in full lines in Fig. 25 is adapted for this purpose. If the rotor is intended for normal operation with the blades fully extended, the housing is preferably arranged yto enclose the drums, as shown in dotted lines in Fig. 25.

The operation of this embo'diment of the invention is as follows: The shaft 255 being driven by the engine, the clutch 256 is engaged and the rotatable system is brought up to a high speed.

-, In the embodiment of Ithe invention shown, the

rotation is in the clockwise direction, as viewed in Fig.- 27. 'I'he clutch 258 is then engaged and owing to the fact that the ratio between the gears 251 and 24,9 is higher than the ratio between the pinion 252 and the gear 25|, the worm 243 is driven at a higher speed than the sleeve 25| and in the same direction. The worm 248 consequently drives the gear 210 and causes the drums 253 to rotate in opposite directions so as to feed out the blades from the top vof the coil.

'Ihe blades are held outwardly in the radial direction by centrifugal force. During the'extension of the blades, power is supplied to the rotating system by the engine. When the blades are fully paid out the clutch 258 is disengaged and the engine is accelerated to impart flight speed to the rotor. When the rotor nearly sustains the weight of the aircraft, the clutch 254 is disengag'ed and the propeller of the aircraft is .ac-`

celerated so as to move the aircraf-t forward so that it takes off. The rotor is then driven by the air forces in well known autogyro fashion. After speed is attained, the brake 21| is applied, with the result that the blades are drawn inwardly owing to the difference of rotation of the sleeves 2.41 and 258, and when the effective length of theblades is 'adjusted for high speed flight the brake 21| is released. The release of the brake 21| is effected at a time when one of the vertical pivots 232 is located near each drum. t For low' speed landing the blades may again be.Y

muy' projected by engaging the clutch 258 for a suitable interval. The rotation of the system has the effect of rotating the worm 248 at a higher speed than the system through gears 25|, 252, 251 and 249 to pay out the blades. Immediately after landing the brake 21| may be applied and the blades will wind up owing to their momentum, and the rotation of the sleeve 250 relative to the sleeve 241. 'I'he machine can then tion. f

It will be noted that the worm drive is irreversible so that the drums are automatically locked in any position they may be in, and that positive actuation of the nature of differential movement between the sleeves 241 and 258 pro- -duced either by the engagement of the clutch 258 or the application of the brake 21| is necessary to change the extension of the blades.

lbe taxied to any desired point in zero un condi It will be understood that in this embodimentl of the invention, like in the other embodiments of the invention, the stationary mounting of the rotor, in this case the spindle 248, may be mounted for universal adjustment relative to the aircraft in the same manner as suggested inFig. 12, for the purpose of balancing and steering the aircraft.

'Ihe tail plane 68 previously referred to has advantages in both autogyro and helicopter operation. Thus, referring to Fig. 28, the full line position of the blade 39 and tail 68 corresponds4 to Ahelicopter operation in which power is applied to the blade. If the engine of the helicopter fails, the angle of the blades should be reduced so that the assembly may continue to rotate in the s ame direction, as an autogyro, to support the aircraft during descent. `With blades having a considerable degree of torsional flexibility, say around their aerodynamic centers, and equipped y with tail surfaces, this action may be made to take place automatically as follows: While the engine -is supplying power to the blades, air is moved downwardly from above by the action of the lifting surfaces. The relative air flow over the assembly to maintain the rotation of the wings and the aircraft supports itself as a helicopter. However, if the power is interrupted, the aircraft as a whole tends to settle toward the earth under the influence of gravity and the relative air flow slants upwardly relative to the plane of rotation, as shown at C. The lifting surface 39 and tail plane 68 maintain asimilar angle to the relative air iiow and assume the position shown in dotted lines in Fig. 28. The resultant force now.

slants forward with relation to the axis of rotation, as shown at c, and a force'is present which will maintain rotation of the lifting surfaces in the same direction as when power was applied.

Thus, the direction of the resultant force slants backwardly when power is applied and slants forwardly when the application of this power isv interrupted, thus automatically maintaining the rotation of the lifting surfaces in the desired direction and assuring continued and enicient lift for safe descent with a dead motor.

In Figs. 29, 30 and 31, we illustrate an embodiment of the invention in which the tail plane 68 is pivotally mounted by means of rods 231 to the torsionally exible blade 39, at apoint 238 forward of its aerodynamic center at which the force rotating the wing system about its axis of rotation is regarded as being applied. At a 75 point substantially behind the aerodynamic center the rods 23,1 are supported by the blade 39 by means of a compression spring 239 or other resilient means, tending to give the chord of the air foil a certain maximum angle with respect to the tail rods 231. The'larger the air forces, the more the spring will be compressed and the more the chord of the lifting surface will tend to assume a position roughly parallell to the tail rods 231, as seen in Fig. 30. The relative motion between the blade 39 and the rods 231 may be limited by stops 240.

As vthe air forces increase with relative air speed, the angle of the lifting surface 39 when rotating around an axis which moves forward through the air will tend to atten out on the upwind side, thus decreasing the lift` while on the downwind side the angle will increase, thereby tending to equalize the lift on the upwind and downwind sides of the axis of rotation.

A damping device should be included between the blade 39 and tail supportmg rods 231 so that energy will be consumedwhen a displacement between these members occurs, thus `tending to vdamp out undesired oscillations. This damping means may consist of a number of spring washers interposed between the pivot members on the blade 39 and on the forward ends of the rods 231. Y

The rods 231 may be pivoted to' the interior of the blade 39 and may project therefrom through slots 242. The stops 240 and springs 239 are also preferably located within the blade 39. If desired, a weight 24| may be carried at or near the forward edge of the blade 39 to counterpoise the weight of the tail plane assembly.

Although the invention has been disclosed in connection with the specific details of preferred embodiments thereof it must be understood that such details are not intended to be limitative of the invention except in so far as set forth in the accompanying claim.

We claim:

1. In an aircraft, a rotating wing system thereon, having a wing of airfoil section flexible in at least one direction, at least one drum permanently located adjacent the axis of rotation of the rotating wing system, around which said wing may be wound for compact storage, said wing being of stable section, having its center of gravity and elastic axis close to its aerodynamic center, and means for inherently damping said wing, said wing having its chord and thickness increasing from its tip towards its root whereby it is rendered inherently resistant to twisting around its spanwisetorsional axis.

2. In an aircraft, a rotating wing system mounted thereon, having a plurality of exible airfoil section wings, means at the inner ends of said wings around which they may be wound into compact coils for storage, and means including weight means adjacent the forward parts of the wings effective to locate the center of mass close to the aerodynamiccenter when the wings are extended, to prevent twisting thereof about their torsional axes.

3. In an aircraft, a revolvable drum mounted thereon, a plurality of airfoil section wings flexible in at least one direction mounted upon said drum, means for rotating said drum so that said wings will extend outwardly from said drum supported by centrifugal force and their `own lift, means including weight means located adjacent the forward parts of the wings, bringing their centers of mass adjacent 'their aerodynamic centers, and means for winding up said wings in Aal coil around said drum for compact storage.

4. In an aircraft, a revolvable drum mounted thereon, with its axis in Aa generally vertical position, a plurality of airfoils fastened to said drum with their chords parallel to the axis of said drum, means revolvable with said drum for twisting said airfoils so that their chords are generally perpendicular to the axis of said drum at a short distance therefrom, means for preventing twisting of the extended wings around their torsional axes, and means for winding said airfoils up around said drum in a coil with their chords parallel to the axis of said drum for compact storage.

v5. In an aircraft, a rotating wing system mounted thereon, said wing system comprising a plurality of flexible wing members held in position during rotation by centrifugal force and their own lift and tending to fall to the ground when rotation ceases, weight means external to and forward of the wing members fork preventing twisting of said wing members about their torsional axes, means for winding said wing members into coils of small diameter operable before rotation ceases to support and store them while not rotating, and -means for locking the wing members partly extended. 6. In an aircraft, a drum mounted thereon with its axis substantially horizontal, a Aplurality of airfoil section wings extending outwardly from said drum and flexible in at least one direction' and comprising weight means external to and forward of the airfoil sections for preventing twisting of the Wings around their torsional axes, means for rotating said drum in a plane generally parallel to its -axis to cause said airfolls to rotate as a rotating wing system, and means to cause said drum to rotate on its own axis to wind said wings into a compact coil around said drum for storage.

'1. In an aircraft, a drum mounted thereon with its axis substantially vertical, a plurality of grooves in the periphery of said drum constituting threads thereon, an air foil section wing flexible in at least one direction attached to the drum in each thread groove, means for rotating said drum around its axis to rotate said wings as a rotating wing system, and means for causing said wings to roll upon said drum, the front edge of each wing entering into and `following each thread groove for compact storage.

8. In an aircraft, a drum mounted thereon withr its axis substantially vertical, a plurality fo grooves in the periphery of said drum constituting threads thereon, ible in at least one direction attached to the drum in each thread groove, means forrotating said drum around its axis to rotate said wings as a rotating wing system, means for causing said wings to roll up on said drum, the front edge of each wing entering into and following each thread groove for compact storage, and means for maintaining said wings in at least one intermediate position partly wound up and partly extending.

9. In an aircraft, a plurality of air foils extending outward in a generally radial direction from a hub around which they rotate, each said air foil comprising a series of sections hingedly connected together, and rotatable means for winding said air foils into a coil by bending them relatively at said hinged connections for-y compact storage.

an air foil section wing ex- 10. In an aircraft, a plurality of air foils con-'75 sisting of a series of rigid sections, hinge means pivotally connecting the sections together so as to prevent relative torsional movement between adjacent sections, said airfoils extending outwardly in a generally radial direction from a central axis around which they rotate, and means for winding said air foils into a coil by bending them in a direction in which they are flexible for compact storage. Y

11. In an aircraft, a plurality of air foils extending outwardly in a general radial direction from a central axis around which they rotate, the chords of said air foils lying in the general direction of the plane of rotation, said air foils being flexible in the direction of their plane of rotation, and rotatable means for winding up said air foils in this direction into small compass for storage.

12. In an aircraft, a plurality of air foils extending outwardly in a general radial direction from a central axis around which they rotate, the chords of said air foils lying ,in the general direction of the plane of rotation, each said air foil comprising a series of sections pivoted together to provide flexibility in the direction of its plane ofrotation; rotatable means for winding up the air foils in this direction into the form of compact helices, and power means for imparting torque to said air foils at a point substantially away from said central axis.

13. In an aircraft, a plurality of ilexible air foils extending outwardly in a general radial direction from a central axis around which they rotate and adapted to be held extended by centrifugal force, the chords of said air foils lying in the general direction of the plane of rotation, said air foils having a measure of torsional flexibilityl around an axis in the vicinity of their aerodynamic centers, a rearwardly extending tail surface member attached to each of said air foils near its outer end, whereby the tail surface member increases the angle of the chord of said air foils to the plane of rotation when the relative air ilow slants downwardly relative to the plane of rotation, and decreases the angle of the chord of said air foil relative to the plane of rotation when the'relative wind slants upwardly relative to the plane of rotation.

14. In an aircraft, a plurality of air f oils ex\ tending outwardly in a general radial direction from a central axis around which they rotate, the

chords of said air foils lying in the general direc-- tion of the plane of rotation, rotatable means for winding said air foils into coils, said air foils having a measure of torsional flexibility around an axis in the vicinity of their aerodynamic centers, and tail surface ,members located behind and beyond said air foils and supported therefrom.

15. In an aircraft, a plurality of air foils extending outwardly in a general radial direction from a central axis around which they rotate, the chords of said air foils lying in the general direction of the plane of rotationfsaid air foils being capable of winding into a coil and having a measure of torsional flexibility around an axis in the vicinity of their aerodynamic centers, and tail.

surface members connected to said air foils so as to be dragged behind said air foils, the chords of said air foils lying in the general direction of their plane of rotation but being urged by said tail surface members to a position in which the resultant of the airforces on said air foils slants forward with relation to said central axis when the relative windfcomes from below the plane of rotation, and to a position in which the resultant of the air forces slants backward with vrelation to the axis of rotation when the relative wind comes from above said plane of rotation.

16. In an aircraft, a plurality of airffoils extending outwardlyin a general radial 'direction from a central axis around which they rotate, the chords of said airfoils lying in the general direction of the planel of rotation, said air foils having a measure of torsional flexibility around an axis in the vicinity of their aerodynamic nters, and tail surface members connected to said air foils so as to be dragged behind said air foils, said tail surface members being pivotally attached to said air foils forward of the aerodynamic center of said air foils, means .resiliently connecting said air foils to said tail members behind said aerodynamic centers so as to urge said air foils to assume a positive angle with said tail members.

17. In an aircraft, a plurality o'f air foils extending outwardly in a general radial direction from a central axis around which they rotate, the chords of said air foils lying in the general direction of the plane of rotation, said air foils having a measure of torsionalfiexibility around axes in the vicinity of their aerodynamic centers, tail surface members connected to said air foils so as to be dragged behind said air foils,` means for pivotally connecting said tail members to said,

air foils forward of the aerodynamic centers of said air foils, and means resiliently connecting said tail members to said air foils behind said aerodynamic centers whereby said air foils are urged to assume a positive angle with said tail members, and means for frictionally damping the relative motion between said air foils and said tail members.

18. In an aircraft, a plurality of air foils extending outwardly in a general radial direction from a central axis around which they rotate, the chords of said air foils lying in the general direction of the plane of rotation, said air foils being flexible in the direction of `their plane of rotation, power means for imparting torque to said air foils, and resilient means resisting the` flexing of said air foils in a direction opposite to their direction of rotation.

19. In an aircraft, a plurality of air foils extending outward in a generally radial direction from a central member with which they rotate. each said air foil comprising a series of sections hingedly connected together, means forwinding said air foils into a coil by bending them relativelyv at said hinged connections for compact storage, and means for frictionally damping the motion of one section relative to another'section.

20. In an aircraft, a plurality of air foils extending outward in a generally radial direction from Aacentralmember with which theyv rotate,

each said air foil comprising a series of sections hingedly connected together, means for winding said air foils into a coil by bending them relatively at said hinged connections for compact storage, means for frictionally damping the mostorage, means for frictionally damping the motion of'one section relative lto another section, u 

